Eighty-five years ago this month, the September 1939 issue of Radio Craft carried the plans for this receiver, which the magazine dubbed the tiniest ham receiver.

The three-tube (including rectifier) set had a regenerative detector and one stage of audio amplification to drive a set of headphones. It tuned 9.5 through 700 meters with a set of six coils, meaning that it tuned the entire shortwave spectrum, the broadcast band, and could even pull in SOS calls on 600 meters (500 kHz).

As with many of these designs, it featured a hot chassis, so care must be taken before plugging it in to the power socket.